Studies on gonococcal surface components during the past year focused on mechanisms by which these bacterial pathogens alter the structure of their pili and on the effects that lipooligosaccharide (LOS) and opacity- associated (Opa) outer membrane protein constituents exert on gonococcal surface properties. Major recent findings include demonstration that pilin changes that follow transformation with DNA contain pilE (expressed pilin structural gene) are complex, often representing a mixture of transformation and intragenomic recombinations. Gonococcal surface properties are being explored in several ways, including use of Doppler electrophoretic light scattering technology to net cell charge. Both LOS and Opa constitution influence cell charge. The charges imparted by members of the repertoire of 10+ Opa proteins expressed by a single strain has been corroborated by examining E. coli that express the analogous but recombinant genes. LOS and Opa phenotypes also influence cell hydrophobicity. These physical characteristics of gonococci correlate relatively well to the phagocysis of these organisms by human neutrophils in vitro. Additional studies in this laboratory includes investigations by a Guest Worker (R. Judd) on a 44-kD protein that has penicillin binding properties in gonococci and the beginning efforts of a newly-arrived staff member (R. Ankerbauer) to dissect the iron binding components and mechanisms of pseudomonas species.